So far I've only driven MDM and Euro MDM, with one session with DSC off (before I got Euro MDM). I enabled Euro MDM when I saw regular MDM interfering at times when neither I nor my instructor felt it was necessary, which told me that it was time to reduce the safety net. Now having run a few weekends with Euro MDM, I very seldom see it intervene. There have been 2-3 occasions where I knew it intervened because I messed up (and I was grateful for the assistance on those occasions), and a couple times where I saw it and didn't feel I'd done anything wrong. I'm also told that MDM will occasionally intervene without lighting up the dash, which I wish weren't the case personally.

At the end of the day it would be amazing if there were some way to gather telemetry data that showed where and in what way MDM intervened (cutting throttle, braking wheels, etc) while looking at videos and maps -- and (I know this is pie in the sky) see what would have happened in those situations if MDM hadn't been there for you.

For me personally, I don't feel that Euro MDM is "intruding" on my track driving at my current skill level, so I'm leaving it on for the time being as additional insurance. I know a few people in the top run groups of the HPDEs I attend that do the exact same thing. I've found that MDM and Euro MDM can be effective teaching tools so long as you pay attention to when it intervenes and analyze why rather than relying on it to let you get away with driving like an idiot; it also helps me get more comfortable pushing the envelope since I know that if I go too far, there's still a bit of a safegaurd. If I do ever turn it off completely, I will of course scale back my aggression to re-learn the car so that if it turns out MDM had been silently letting me get away with something that isn't possible with everything off, hopefully I'll notice at lower speeds.

I have done a lot of tracking with Euro-MDM on (50+ track days). Just ask all the guys who make fun of me!!!! (YOU KNOW WHO YOU ARE!!!!! )

When moving fast, Euro-MDM absolutely prevents you from getting on the gas until after the apex. People who watch my videos comment all the time that I get back on the gas late after a corner. I have also tracked DSC-off, so I can tell you with 100% certainty, that Euro-MDM is holding back the power until you are after the apex. Now, if it's braking mid-corner, then as others have said, you've done something that the computer is worried will induce a spin---and the computer is pretty good at what it does. It's pretty amazing what you can recover from when a computer can brake individual wheels.

Euro-MDM, while allowing more leeway than the standard USA version, still does not like much sideways movement. It kills power pretty quick and will grab a certain corner's brake to get you back.

Now, that said, you don't have to be slow due to Euro-MDM. I go plenty fast. It is very possible to drive fast without it killing your times. But you have to drive in a way that doesn't trigger it. Usually, that means clean driving.

I'm at 1:57 at Buttonwillow with Euro-MDM on, and despite all the crap people give me, I wouldn't be sub-2 minutes if traction control was kicking in all the time. I've had an AIM solo tied into my CAN buss like Ti-Jean. Even on fast laps, it only nudges the brakes a couple times. But it very consistently holds back power until after the apex.

As others have said, if traction control is braking in middle of turns, it means you came in too hot, maybe turned the wheel too much then held the wheel closed too long, and then the computer was like.....uh no. Euro-MDM is EXTREMELY effective at keeping the rear of the car behind you.

I've been experimenting with DSC-off at a few tracks lately. (I only do it when no other cars are around me.) It is interesting having access to the power much earlier at the apex. It's quite nice actually. And at Big Willow a week ago, it was an interesting moment as I got loose in Turn 9 at 90mph. I caught it fine and went on my merry way, but one needs to really really be on guard at all times with DSC-off---especially when you have a blower in the car, as I do. The E9x M3 is pretty easy to rotate with DSC off. In the end, I make no excuses for driving with Euro-MDM on. And my buddies give me a pretty hard time and try to shame me into switching over. I'm immune to peer pressure, but I am enjoying experimenting with DSC-off on my own schedule. As far as what you're experiencing, as others have said, I'd say you need to brake more before the corner and you won't find MDM braking mid-turn.

Interestingly, many guys are showing up at the track now with wings and front lips on their E9x M3's. I've had the opportunity to drive the previous EAS shop car at Buttonwillow with the wing on it. That car didn't have MDM because it had no nav screen. Your choices were either DSC-full-on or DSC-off. I drove with it off. You know what the wing feels like? Traction Control!! The wing holds that rear down and it feels just like traction control.

Forum member DD GT3 RD was at Big Willow with a big wing for the first time a week ago. One of his comments was that he's used to being able to kick the rear out on Turn 5 and drift it without any aero on the car. With the wing, he couldn't break the rear free in that turn. I think he dropped like 2-3 seconds on his first session with the wing. Pretty cool to see. Ran like a 1:30.9 or something on RS3's!

Wouldn't say it's TC cause once you spin it won't do anything to save you but I only had a rear wing and no front aero and the cars ass would stick everywhere. I would floor it thru turns and wouldn't break loose, only could on the uphill angled turn 3.
Now hopefully with a balanced car (equal front aero) this won't be the case.

I always say do what makes YOU happy and safe. I used to drive with mdm but now I can't stand it and find nothing as fun or comparable to driving with TC off. It's just completely different, messing up and catching yourself, drifting etc. but you can enjoy yourself plenty with it on. Gabe kills it with it on euro mdm so there you go.

What's the benefit of apexing early? I get that it would be POSSIBLE to apex early without incident if you can get enough throttle steer to rotate the car enough to exit the corner successfully, but just thinking about it (and having started to read Ross Bentley's awesome Ultimate Speed Secrets book), I can't think of the advantage of an early apex for most corner scenarios over a geometric line or even a late-apex line to length the upcoming straightaway. But I also know that you know what you're talking about, so I'm curious.

Earlier apex (not early) is probably a better way to describe it. You have 3 inputs to influence the car...steering, brake, and throttle. Of the three...which one is the only one that makes you go faster? By sliding (generating slip angle in the tires) the car to rotate under throttle...not turn...the car...you are going faster. So now you can 4 wheel steer the car instead of using just the two front wheels which means more overall grip.

Threshold braking puts more weight over the front wheels. By turning in you put all of the weight on the outer front tire. Now you want your rear wheels to accelerate but most of the load has been transferred to the front so there's no grip. So the car wants to oversteer. The driver who's already rotated the car under throttle can get on the throttle more aggressively and sooner. Although they may break earlier and longer, their apex and exit speed is probably significantly higher. That delta multiplies as you get further down the straight relative to HP. If you follow a car in the red and instructor group the tires look like they are sliding across the pavement...that's slip angle. There's a time and place for late apexes but not always.

The E46M3 rear tires toe out as the rear squats which makes the rear twitchy and harder to control. When you hang on the rear suspension like a monkey on the alignment stands you'll see the rear to go from toe in to toe out. I haven't confirmed this yet but I believe the E9X M3 rear tires toe in when the rear squats which makes the car want to straighten up. If you ever try to drift an E9X M3 is REALLY hard to keep it sideways because you really have to give it a lot of throttle to keep the rear tires spinning. Which is why you can really dial in a lot of slip angles (slide) into the tires and it really benefits lap times...because the car is really easy to control at and beyond the limit.

I have done a lot of tracking with Euro-MDM on (50+ track days). Just ask all the guys who make fun of me!!!! (YOU KNOW WHO YOU ARE!!!!! )

When moving fast, Euro-MDM absolutely prevents you from getting on the gas until after the apex. People who watch my videos comment all the time that I get back on the gas late after a corner. I have also tracked DSC-off, so I can tell you with 100% certainty, that Euro-MDM is holding back the power until you are after the apex. Now, if it's braking mid-corner, then as others have said, you've done something that the computer is worried will induce a spin---and the computer is pretty good at what it does. It's pretty amazing what you can recover from when a computer can brake individual wheels.

Euro-MDM, while allowing more leeway than the standard USA version, still does not like much sideways movement. It kills power pretty quick and will grab a certain corner's brake to get you back.

Now, that said, you don't have to be slow due to Euro-MDM. I go plenty fast. It is very possible to drive fast without it killing your times. But you have to drive in a way that doesn't trigger it. Usually, that means clean driving.

I'm at 1:57 at Buttonwillow with Euro-MDM on, and despite all the crap people give me, I wouldn't be sub-2 minutes if traction control was kicking in all the time. I've had an AIM solo tied into my CAN buss like Ti-Jean. Even on fast laps, it only nudges the brakes a couple times. But it very consistently holds back power until after the apex.

As others have said, if traction control is braking in middle of turns, it means you came in too hot, maybe turned the wheel too much then held the wheel closed too long, and then the computer was like.....uh no. Euro-MDM is EXTREMELY effective at keeping the rear of the car behind you.

I've been experimenting with DSC-off at a few tracks lately. (I only do it when no other cars are around me.) It is interesting having access to the power much earlier at the apex. It's quite nice actually. And at Big Willow a week ago, it was an interesting moment as I got loose in Turn 9 at 90mph. I caught it fine and went on my merry way, but one needs to really really be on guard at all times with DSC-off---especially when you have a blower in the car, as I do. The E9x M3 is pretty easy to rotate with DSC off. In the end, I make no excuses for driving with Euro-MDM on. And my buddies give me a pretty hard time and try to shame me into switching over. I'm immune to peer pressure, but I am enjoying experimenting with DSC-off on my own schedule. As far as what you're experiencing, as others have said, I'd say you need to brake more before the corner and you won't find MDM braking mid-turn.

Interestingly, many guys are showing up at the track now with wings and front lips on their E9x M3's. I've had the opportunity to drive the previous EAS shop car at Buttonwillow with the wing on it. That car didn't have MDM because it had no nav screen. Your choices were either DSC-full-on or DSC-off. I drove with it off. You know what the wing feels like? Traction Control!! The wing holds that rear down and it feels just like traction control.

Amen. I consign everything said here from an east coast track perspective. Even the part about the wing..... Which I do track with.

Steering with the throttle is fun and the reason why I set my throttle response to normal instead of sport or sport plus. The normal setting allows me to modulate the throttle much easier. The other two settings are like on/ off switches which makes you feel like the car is more responsive on the street but does nothing but make you a bad driver on the track. As dogbone said, MDM doesn't let you get on the power until after the apex, which not only take away the fun factor but prevents you from getting out of a understeer situation, where the right application of gas could have rotated the car back pointing in the right direction. I have Euro MDM, I find it too intrusive to my driving style on VIR. I use it in the rain but then it is more of a security blanket because I smooth out my driving to the point where TC never kicks on.

Earlier apex (not early) is probably a better way to describe it. You have 3 inputs to influence the car...steering, brake, and throttle. Of the three...which one is the only one that makes you go faster? By sliding (generating slip angle in the tires) the car to rotate under throttle...not turn...the car...you are going faster. So now you can 4 wheel steer the car instead of using just the two front wheels which means more overall grip.

Threshold braking puts more weight over the front wheels. By turning in you put all of the weight on the outer front tire. Now you want your rear wheels to accelerate but most of the load has been transferred to the front so there's no grip. So the car wants to oversteer. The driver who's already rotated the car under throttle can get on the throttle more aggressively and sooner. Although they may break earlier and longer, their apex and exit speed is probably significantly higher. That delta multiplies as you get further down the straight relative to HP. If you follow a car in the red and instructor group the tires look like they are sliding across the pavement...that's slip angle. There's a time and place for late apexes but not always.

The E46M3 rear tires toe out as the rear squats which makes the rear twitchy and harder to control. When you hang on the rear suspension like a monkey on the alignment stands you'll see the rear to go from toe in to toe out. I haven't confirmed this yet but I believe the E9X M3 rear tires toe in when the rear squats which makes the car want to straighten up. If you ever try to drift an E9X M3 is REALLY hard to keep it sideways because you really have to give it a lot of throttle to keep the rear tires spinning. Which is why you can really dial in a lot of slip angles (slide) into the tires and it really benefits lap times...because the car is really easy to control at and beyond the limit.

AWESOME explanation! Thanks for this write-up!

I have indeed seen (and felt) red and instructor cars slide in the way you describe. I'm currently Yellow (and Yellow Solo for TWS CCW) and in my own driving I've gotten a glimpse of that next level. I can't do it in every corner or even every time in certain corners just yet, but so far running CCW the places I've been able to replicate what you're describing most often are Turns 6 and 8 -- and when I get it right, my brain goes like this: Wow-I'm-faster-than-my-norm-coming-into-this-turn-I-can-feel-all-4-tires-gliding-across-the-pavement-as-I-add-throttle-oh-my-God-am-I-about-to-run-out-of-track-on-the-exit-nope-phew-wow-that-was-so-incredibly-cool.

The benefits and goals you're describing (sacrificing entry speed to rotate the car earlier and thus get on the power earlier and harder) line up with what I've read and been taught, but those places mention that a later-than-geometric apex is the way to achieve that, since if you come in too early you end up having to tighten up on entry when you should already be straightening out and adding throttle. "Earlier" as you mentioned above is of course a relative term and not to be confused with "early", but in order do what you're describing, it seems that on a simple 90-degree turn, the ideal strategy would be to square it off slightly on entry and then hit the apex a bit PAST the center of the turn (geometric apex). I found this page that basically describes what I'm getting at under the Late Apex heading: http://www.drivingfast.net/techniques/racing-line.htm.

So would an appropriate revision of your point perhaps be "whoever is earlier among the late apexers will be faster"?

On Big Willow I felt TC come on when I made a mistake. On Streets of Willow I felt the TC come on when I was trying to power out of turns and didn't make any big mistakes (I thought). The car would just cut power until completely straight and out of the turn. Euro MDM was definitely interfering. My instructor recommends that I disable DSC next time and work my way up to find the limits of the car without MDM/DSC. They tell me as all the car reviews do that the M3 has a really good chassis and you don't get to really feel that until DSC is off.

I think the engagement of TC depends on the track and your driving style. Whether you are absolutely smooth or want to push the car more and generate some slip. When instructors drove my car, it felt like they were manhandling it and then they would tell me that they were going at 50%. I was like huh? I guess I'm being too gentle. When I got back in the car to push it, TC was lighting up on most corner exits. Just like it was for the instructor.

My plan is to revisit Streets with DSC off and throttle set to Normal. I am going to keep Euro MDM on for Big Willow because the high speed sweepers still creep me out.

I have indeed seen (and felt) red and instructor cars slide in the way you describe. I'm currently Yellow (and Yellow Solo for TWS CCW) and in my own driving I've gotten a glimpse of that next level. I can't do it in every corner or even every time in certain corners just yet, but so far running CCW the places I've been able to replicate what you're describing most often are Turns 6 and 8 -- and when I get it right, my brain goes like this: Wow-I'm-faster-than-my-norm-coming-into-this-turn-I-can-feel-all-4-tires-gliding-across-the-pavement-as-I-add-throttle-oh-my-God-am-I-about-to-run-out-of-track-on-the-exit-nope-phew-wow-that-was-so-incredibly-cool.

The benefits and goals you're describing (sacrificing entry speed to rotate the car earlier and thus get on the power earlier and harder) line up with what I've read and been taught, but those places mention that a later-than-geometric apex is the way to achieve that, since if you come in too early you end up having to tighten up on entry when you should already be straightening out and adding throttle. "Earlier" as you mentioned above is of course a relative term and not to be confused with "early", but in order do what you're describing, it seems that on a simple 90-degree turn, the ideal strategy would be to square it off slightly on entry and then hit the apex a bit PAST the center of the turn (geometric apex). I found this page that basically describes what I'm getting at under the Late Apex heading: http://www.drivingfast.net/techniques/racing-line.htm.

So would an appropriate revision of your point perhaps be "whoever is earlier among the late apexers will be faster"?

That link is way too simple. Take MSRH for example where the road is crowned. So if you follow that link's example in the carousel you'll either never get to the apex or you'll need to slow the car down a lot more than needed. It also ignores the fact that every time you turn the steering wheel you scrub speed. The late apex line forces you to drive further. If you turn in a little earlier and steer the car with the rear tires, you less steering input and you can accelerate earlier and faster while taking a shorter line.

Keep in mind that this is a technique. There are turns that are better late apex'd for certain reasons specific to the corner. Sometimes trailbraking is the answer especially when you want to carry speed after a straight into a corner. There are so many variables in a turn so it is anything but simple.

Here's a good video where you can really see what it looks like when the rear tire is sliding across the pavement.

On Big Willow I felt TC come on when I made a mistake. On Streets of Willow I felt the TC come on when I was trying to power out of turns and didn't make any big mistakes (I thought). The car would just cut power until completely straight and out of the turn. Euro MDM was definitely interfering. My instructor recommends that I disable DSC next time and work my way up to find the limits of the car without MDM/DSC. They tell me as all the car reviews do that the M3 has a really good chassis and you don't get to really feel that until DSC is off.

I think the engagement of TC depends on the track and your driving style. Whether you are absolutely smooth or want to push the car more and generate some slip. When instructors drove my car, it felt like they were manhandling it and then they would tell me that they were going at 50%. I was like huh? I guess I'm being too gentle. When I got back in the car to push it, TC was lighting up on most corner exits. Just like it was for the instructor.

My plan is to revisit Streets with DSC off and throttle set to Normal. I am going to keep Euro MDM on for Big Willow because the high speed sweepers still creep me out.

Which turn is bothering you at big willow? 5?, 4?, or 9? Those are the likely candidates, in order of likelihood from my many laps on that track.

Try to watch how much steering input you have in when you apply the throttle. What the TC is telling you is 1) you entered the turn too fast (slow in = fast out) or you have too much steering input so it cuts throttle off until you scrub speed. See if you can watch these two things the next time you're there and determine if either of them are the cause.

On Big Willow I felt TC come on when I made a mistake. On Streets of Willow I felt the TC come on when I was trying to power out of turns and didn't make any big mistakes (I thought). The car would just cut power until completely straight and out of the turn. Euro MDM was definitely interfering. My instructor recommends that I disable DSC next time and work my way up to find the limits of the car without MDM/DSC. They tell me as all the car reviews do that the M3 has a really good chassis and you don't get to really feel that until DSC is off.

I think the engagement of TC depends on the track and your driving style. Whether you are absolutely smooth or want to push the car more and generate some slip. When instructors drove my car, it felt like they were manhandling it and then they would tell me that they were going at 50%. I was like huh? I guess I'm being too gentle. When I got back in the car to push it, TC was lighting up on most corner exits. Just like it was for the instructor.

My plan is to revisit Streets with DSC off and throttle set to Normal. I am going to keep Euro MDM on for Big Willow because the high speed sweepers still creep me out.

Which turn is bothering you at big willow? 5?, 4?, or 9? Those are the likely candidates, in order of likelihood from my many laps on that track.

Try to watch how much steering input you have in when you apply the throttle. What the TC is telling you is 1) you entered the turn too fast (slow in = fast out) or you have too much steering input so it cuts throttle off until you scrub speed. See if you can watch these two things the next time you're there and determine if either of them are the cause.

TC didn't interfere on big willow as much as it did on streets. On big willow I saw TC come on when I made obvious mistakes like downshifting and accelerating during a turn. I'll keep TC on for big willow, be smooth and test my manhood in those long sweepers.

Good tip on steering and throttle input. I'll watch it. On Streets, I'm pretty sure I'm either not letting my wheel unwind enough on exit before getting on the gas or just giving it too much gas. Problem is you can't really learn the limit with TC on in tight corners. It cuts power aggressively.

It would be great if TC was smart enough to stay on in high speed sweepers, but deactivate in lower speed hairpins and such. That's what I would prefer anyways.

All really good info from other posters here. I highly
recommend turning it off and experimenting when you
have a safe track and the confidence to do so.
If you've been attentive to the limits of MDM and have
learned smooth inputs it's not hard to make the transition.
My driving has taken a huge jump since turning it off and
seems like an essential step for learning better car control.
Throttle steer is FUN!

What's the benefit of apexing early? I get that it would be POSSIBLE to apex early without incident if you can get enough throttle steer to rotate the car enough to exit the corner successfully, but just thinking about it (and having started to read Ross Bentley's awesome Ultimate Speed Secrets book), I can't think of the advantage of an early apex for most corner scenarios over a geometric line or even a late-apex line to length the upcoming straightaway. But I also know that you know what you're talking about, so I'm curious.

Early apexing may get you trough the corner faster, if you dont run out of the road at the exit. I wouldnt recommend early apexing anywhere for novace, intermidiate, or even advanced HPDE drivers.